unlink

, unlinkat

- remove directory entry

Synopsis

#include <unistd.h>
intunlink(const char *path);

intunlinkat(intdirfd, const char *path, intflag);

Description

The unlink() function removes a link to a file. If path names
a symbolic link, unlink() removes the symbolic link named by path and
does not affect any file or directory named by the contents of
the symbolic link. Otherwise, unlink() removes the link named by the pathname
pointed to by path and decrements the link count of the file
referenced by the link.

The unlinkat() function also removes a link to a file. See fsattr(5).
If the flag argument is 0, the behavior of unlinkat() is the same
as unlink() except in the processing of its path argument. If path
is absolute, unlinkat() behaves the same as unlink() and the dirfd argument is
unused. If path is relative and dirfd has the value AT_FDCWD, defined
in <fcntl.h>, unlinkat() also behaves the same as unlink(). Otherwise, path is resolved
relative to the directory referenced by the dirfd argument.

If the flag argument is set to the value AT_REMOVEDIR, defined in
<fcntl.h>, unlinkat() behaves the same as rmdir(2) except in the processing of
the path argument as described above.

When the file's link count becomes 0 and no process has the
file open, the space occupied by the file will be freed and
the file is no longer accessible. If one or more processes have
the file open when the last link is removed, the link is
removed before unlink() or unlinkat() returns, but the removal of the file
contents is postponed until all references to the file are closed.

If the path argument is a directory and the filesystem supports unlink()
and unlinkat() on directories, the directory is unlinked from its parent with
no cleanup being performed. In UFS, the disconnected directory will be
found the next time the filesystem is checked with fsck(1M). The unlink() and
unlinkat() functions will not fail simply because a directory is not empty. The
user with appropriate privileges can orphan a non-empty directory without generating an
error message.

If the path argument is a directory and the filesystem does not
support unlink() and unlink() on directories (for example, ZFS), the call will
fail with errno set to EPERM.

Upon successful completion, unlink() and unlinkat() will mark for update the st_ctime
and st_mtime fields of the parent directory. If the file's link
count is not 0, the st_ctime field of the file will be marked
for update.

Return Values

Upon successful completion, 0 is returned. Otherwise, -1 is returned, errno
is set to indicate the error, and the file is not unlinked.

Errors

The unlink() and unlinkat() functions will fail if:

EACCES

Search permission is denied for a component of the path prefix, or write permission is denied on the directory containing the link to be removed.

EACCES

The parent directory has the sticky bit set and the file is not writable by the user, the user does not own the parent directory, the user does not own the file, and the user is not a privileged user.

EBUSY

The entry to be unlinked is the mount point for a mounted file system.

EFAULT

The path argument points to an illegal address.

EINTR

A signal was caught during the execution of the unlink() function.

ELOOP

Too many symbolic links were encountered in translating path.

ENAMETOOLONG

The length of the path argument exceeds PATH_MAX, or the length of a path component exceeds NAME_MAX while _POSIX_NO_TRUNC is in effect.

ENOENT

The named file does not exist or is a null pathname.

ENOLINK

The path argument points to a remote machine and the link to that machine is no longer active.

ENOTDIR

A component of the path prefix is not a directory or the provided directory descriptor for unlinkat() is not AT_FDCWD or does not reference a directory.

EPERM

The named file is a directory and {PRIV_SYS_LINKDIR} is not asserted in the effective set of the calling process, or the filesystem implementation does not support unlink() or unlinkat() on directories.

EROFS

The directory entry to be unlinked is part of a read-only file system.

The unlink() and unlinkat() functions may fail if:

ENAMETOOLONG

Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}.

ETXTBSY

The entry to be unlinked is the last directory entry to a pure procedure (shared text) file that is being executed.